I'm not especially bright, especially with electrical stuff, so bear with me.

TSP/F got me interested in battery backup, so I built my first one a few years ago.

It was basically two 6V 220Ah GC2 batteries from Costco, an oversized inverter, a so-so 4A 3-stage charger, and some cables and 400A fuse, all inside a flip-top crate on a dolly. I took pretty good care of it at first, checking the fluids regularly, using the battery every couple months, but most of the time it just sat in the utility room and pissed my wife off every time she had to walk by it. Then, one day while making a rare trip to Walmart, I noticed the big 55A Schumacher that I'd heard about on one of the Steve Harris episodes, so I bought it.

I managed to boil off enough water to expose the plates by the third time I used it, which instantly reduced the capacity of my battery bank to about 75% of what it had been. I was mad at the charger, but mostly just mad at myself for being so stupid for charging a 220Ah battery bank at 55A. So I decided to try something different and go with an AGM battery, different charger, and different container.

I wound up with a 150Ah Lifeline AGM battery and a 1500W inverter in a vertical rolling Pelican case. I also got a 26A Genius charger for bulk charging, and a smaller 1A Genius to keep it on float.

Overall, I was pretty pleased with the system in terms of its compactness and the performance of the battery and chargers. It was nearly maintenance free and a bit easier to move around than the previous setup, but still pissed my wife off every time she had to walk by it (of course, now there were two monsters in the utility room).

I then decided to try something inside my vehicle and decided to go with a couple of U1 batteries in parallel, an inverter, and an ISOpwr unit between the car battery and the auxiliary battery.

I was able to fit everything into a milk crate and used the 12V outlet in the back of my vehicle, instead of pulling another separate cable directly from the car battery. It worked fine for a couple of years and all I ever did was check the battery voltage every now and then and made sure that charging light came on when the engine was running. When I dismantled the system a few months ago, I was pleased that both batteries were functioning well when I tested them, which was kind of surprising because I've ruined several of the Universal Battery products before.

The downside was that I wanted a bit more capacity and started thinking of putting my 150Ah AGM in the car instead. The big problem, though, was I wanted something smarter than the ISOpwr unit for charging the AGM, which seems to have done very well spending most of its life floating on a charger. I then started looking at ways to have the AGM battery hooked to a charger, which was constantly powered by the U1s, whether the vehicle was running or not, and continue to use the ISOpwr to charge the U1s when the engine was running.

Basically, the PWRgate is designed as a battery backup for ham radio operations, which charges the battery from a DC power supply and can instantly switch to the battery if the power supply goes down. It has a fairly sophisticated 3-stage charger and has a jumper setting for AGM charging, but it requires that the power supply voltage be 14.5V in order to reach peak voltage during the charge cycle. What I needed was a way to boost the voltage coming from the pair of U1 batteries and use that as the power supply input for the PWRgate. This led me to experimenting with an inexpensive unit from Amazon and building one into a case with Anderson Powerpole connectors that would join the ISOpwr and PWRgate units.

After I bench tested the various components (and blowing up my PWRgate, necessitating shipping it in for repairs), I had to figure out what kind of container I was going to use to hold everything in the back of my vehicle. I was torn between using another Pelican case or a rack mounted roadie case, but in the end went with something pretty mundane.

I've had this cheapo plastic four-drawer storage thingy for at least 12 years. As much as I'd like to get rid of it, I still wind up putting it back in because it's so useful, so I decided to put the batteries in the bottom drawer and everything else in the drawer just above it.

The batteries fit perfectly, but I did have to get a little creative with fusing all three batteries at the positive terminals. I wound up bolting the fuses directly to the terminals, instead of using the usual fuse holders for this type of fuse.

Next, I needed a way of organizing the inverter, ISOpwr, voltage booster, and PWRgate in the second shelf.

I found a perfectly sized piece of wire-shelf cutoff and discovered that I could wedge the ISOpwr and PWRgate units onto it to act as legs, hold them in place with zip ties, and have an inclined shelf that allows the inverter to breathe, as well as improves access to the switch and sockets. Plus, reading the status lights through the clear plastic drawer fronts is easy and can be done without having to pull out the drawer.

I used 2 gauge wire from the 150Ah battery directly to the inverter, and a fused 10 gauge wire from the PWRgate for charging. I set the maximum charge at 4A. The two U1 batteries were wired in parallel with 4 gauge wire and a 10 gauge connection to the ISOpwr. I duct taped a meter to the drawer front so I can check the voltage of the U1s and make sure they're not getting too low.

For the last 10 days everything's been working great. The PWRgate is getting the constant 14.5V it needs and the AGM battery is staying on float. The voltage on the U1s hasn't gotten below 12.3V and they're staying charged with just the short little bit of driving I do, even when I don't go anywhere for 3 or 4 days. The current overhead while in float is less than 100 mA, with half of that coming from the ISOpwr, which seems kind of high since it's not doing much when the vehicle is off, but that's still much lower than any of the other options I experimented with.

The next stage will be to add a RigRunner for DC power distribution, USB outlet, and NiMH charger.

But what does it power?(maybe I missed where you said what it was)The real trick is to balance charging and discharging because a battery is damaged just as easily buy constant charging as it is discharging...the positive plates are damaged buy constant charging ,unless balanced by occasional discharge (I run equipment from my battery system at least monthly) Constant charging can ,and will,oxidize and corrode the positive plates in the battery.So even with a good 3 stage charger I suggest you exercise your CHEMICAL power storage at least monthly.

Hey ,don't just take my word for it ...look it up...I am still confused about the charging a battery from another battery that is itself charged from another battery....when my mobile power is used...I just crank the car and idle at 1 gallon per 2 1/2 hours and let my primary auto battery/alternator do the work .

Big, and expensive mistake with the 55A charger, waaay over kill and not a smart charger. I can tell you the story of boiling a battery overnight at the shop I worked at, rotten egg smell for the next 2 daze!

Anywho, I really really like the final setup, congrats and hope it last a long time for you!

Talk about timing I just yanked one those inverters out today ( 2300watt same brand ) .it wasn't doing the job. Installed a 5000/10000 watt inverter . System has 4 golf cart batteries already. To this I added a battery isolator and fuse . This is installed in a Ford E350 . This allows them to charge while driving and to use it stationary without draining their starting batteries. What does it run you ask ? 2 chest freezers ,a refrigerator, a milkshake machine and a snowcone machine.. This is one of those ice cream trucks that runs around the neighborhoods.

What are the advantages to this approach vs. using a smart isolator like the Cole Hersee 48530?

One thing I see is that this will give you the ability to charge the AGM from others (i.e. just swap out the U1s with whatever you have charged). Another is that the AGM will always be near maximum voltage which could be an advantage with some equipment which is sensitive to voltage level. On the downside this is more complicated.

What are the advantages to this approach vs. using a smart isolator like the Cole Hersee 48530?

Honestly, I don't know enough to have a good answer for you.

I got licensed for ham radio a few years back, and, while I'm a crappy ham and don't get on the air much, it has exposed me to the 12V DC power products used by those in the ham-isphere. The ISOpwr and PWRgate are made by West Mountain Radio and use the Anderson Powerpole connector, which is rapidly becoming the defacto industry standard. I made the decision to standardize my DC stuff around these connectors as much as possible, and using the WMR products made it really easy to swap things in and out in a modular fashion, which provides a simple way to experiment.

The only real advantage is no moving parts . The isolater I used was a Cole Hersee 48160 . I still remember when those smart idolaters came out . I did some installs for the SO. So they could run the lights and radio on wrecks scenes with the motor off with a battery in the trunk and still be able to start . Then 6 months later massive recall.

It's been six months since the system went into the vehicle and I thought it was time to do some testing.

One of the things I've noticed is that with the small amount of driving I do, I cannot keep the intermediate pair of U1 SLAs adequately charged, so I've spliced in a dongle so I can hook up to an AC charger to top things off when I think about it. So far, despite going several weeks without much use of the vehicle, the intermediate batteries have maintained sufficient charge (never below 11V, and usually not below 12V) to keep the AGM on float via the DC voltage converter and PWRgate unit, which was the whole point of this experiment. So I figured it was time to test the capacities and see what damage the batteries had suffered, thus far.

I used my West Mountain CBA IV to test both my Lifeline AGM and the pair of U1s in parallel, without removing them from the vehicle, and compare the measured capacities to the tests I'd run before the vehicle installation. Here's picture of the mess it took to get all that done. Notice the extra cooling fan blowing directly onto the CBA, which was necessary given that I ran it at a constant 150W and it isn't typically able to sustain more than a 100W load without overheating and shutting down mid test.

The results for the Lifeline AGM, which is rated at 150Ah, was 137Ah at a constant 150W draw down to 11V. My testing 6 months ago yielded 139Ah at the same draw, so I'm pretty happy with that. This battery is nearing the three year mark and I still haven't killed it, which is a miracle for me. I'm very much impressed with these batteries and think the higher premium may actually be worth it.

The result for the U1s wasn't great, but it wasn't that bad, either, especially given the conditions they've been under. Previous testing of each one separately delivered a capacity of 30Ah at a 100W draw. This battery is rated at 35Ah. Testing two in parallel at 75W yielded a 50Ah capacity, which is a significant decrease. But, that was kind of the point of this design, to put a lesser cost battery in between the alternator and the high cost AGM. So I'm happy.

One of the things I need to look into, though, is why the 12V outlet in the back of the vehicle is unable to output more than 3A to the ISOpwr unit for charging the U1s. The socket states it's rated for 120W, which is roughly 10A, so why is it only putting out a third of that? I don't really want to pull a separate cable through the firewall and into the back, but that would probably be the best way to guarantee sufficient charging current. I'll keep an eye on it, though. I'll be driving a bit more now, so I may have an easier time keeping things topped off.

The resistance in the length(and size) of the wire to the front of the vehicle is your primary limiting factor.

how long are they and what guage ?

In the same vein, since you are new to electric theory FL, the connector on either end of this long cable can do the same thing, cause a bottleneck.

IF, and we dont know it is so yet, you have too high of resistance due to overly thin guage for the length, or rarer the wrong connctor or poor job connecting, you can have problems in use, you might overheat the wire and melt it due to trying to draw too much power thru it ( this is what a standard electric stove or electric resistance heater does, too much resistance means the conductor will get hot, very hot potentially, and unlike my electric stove element copper wire has a lower melting point) some tools running on too low of amps will overwork their motors and it will shorten their lifespan ( my ex borrowed what was a very good, high powered weed wacker from me and used it with one extension cord plugged into the other and maimed the motor)

So, since you want this ready fr an emergency, I think you should find out why you cant get the expected amps out hte other end

I really like the idea of the PWRGate. But for the cost I can get another battery. I have PowerPoles on most everything now, so it's just a power off and hot swap of connectors.That all said, I would accept one if given as a gift

Thanks guys, I think I agree with all of you. Still need to look into the car's outlet issue thoroughly, although I have confirmed all my wiring and connectors don't get hot to the touch. What's the likelihood that Honda wired a 12V outlet rated for 120W with too skimpy of a cable? What's the likelihood of my car burning up if it hasn't already?

Thanks guys, I think I agree with all of you. Still need to look into the car's outlet issue thoroughly, although I have confirmed all my wiring and connectors don't get hot to the touch. What's the likelihood that Honda wired a 12V outlet rated for 120W with too skimpy of a cable? What's the likelihood of my car burning up if it hasn't already?

When I got my used Acura TL (it's basically a fancier Accord) I ran 12awg wire from the battery posts through the firewall into the cabin terminating with 30amp powerpoles. I initially did it for ad-hoc ham radio installs, but realized I could potentially recharge my cranking battery (though slowly). For the radio, that wiring should safely handle 30amps, which is more than enough even a 100w HF rig at full power.

Thanks guys, I think I agree with all of you. Still need to look into the car's outlet issue thoroughly, although I have confirmed all my wiring and connectors don't get hot to the touch. What's the likelihood that Honda wired a 12V outlet rated for 120W with too skimpy of a cable? What's the likelihood of my car burning up if it hasn't already?

might be unlkely, but there are ways this could happen, (1) supplier short-cuts them and supplies poor product that actually doesnt meet the car manuacturers' specs (2) the cable and connectors do meet spec., but installation wasnt done properly ( for example, poor crimp or solder area or meachnical; cable cut part way thru during assembly, etc...)

So, when you have time, try to narrow down where the bottleneck happens. I havent taken the time to go thru what you did, but if this was just a car battery to a dashboard OEM connector, I would narrow it down by doing this: Confirm the battery, on its own terminals under the hood, actally supplies the expected amps, and trace the path as well as I could to look for problems after that ( connector on battery, is there another spot that is a junction with connectors? is the cable sound where you can see it, etc.... all the usual stuff ...

Also understand that the average wet cell battery is only viable for about 3 years.I use them till they give out in non-essential spots ,but replace on a three year cycle the more critical batteries as I move tested cells down the chain.

I'd be happy to send you the one I smoked, if you like. It's worked fine since WMR repaired it, but I kind of don't trust it and I never could really narrow down why it failed. I hooked up its replacement the exact same way without incident, but the circuit board and components were different between the new one and the smoked one, so who knows.

When I got my used Acura TL (it's basically a fancier Accord) I ran 12awg wire from the battery posts through the firewall into the cabin terminating with 30amp powerpoles. I initially did it for ad-hoc ham radio installs, but realized I could potentially recharge my cranking battery (though slowly). For the radio, that wiring should safely handle 30amps, which is more than enough even a 100w HF rig at full power.

The more I think about, the more I think this makes the most sense. I've been thinking about moving the batteries forward, between the front and rest passenger seats for a bit better weight distribution, anyways, so I might as well run something more substantial through the firewall from the starting battery and really take full advantage of the extra power. Given the time it takes to troubleshoot that stupid 12V outlet in the back, seems like a better way to go, especially if I'm already moving a bunch of stuff around.

Good idea, also be sure to FUSE at the interconnection point and protect the wire from chafing where it passes through the firewall...also make sure the wire is insulated for high temperature areas.

I think I've got some nice 8 or 10 gauge two-wire stuff that has an outer sheath, kind of similar to Romex, but designed for marine DC use. It might be a bit of overkill, but better too big than too small, right? And I've got a few different fuse options in a drawer to choose from, too.

Would there be any benefit to also installing a switch at the interconnect? I think I've got one those heavy duty blade switches that's rated for high current. I haven't thought through all the ramifications, but if I'm in there anyways....

A fuse should be enough though a quick disconnect or circuit breaker ...or s switch would do OK...the quick disconnect type plug is a solid safety device.And your Marine wire should be fine as most ,by standards, is oil,heat,moisture protected.

Off the battery posts I have in-line fuses for both + and - wires. I improvised a grommet using vinyl tubing and zipties. I then sprayed some foam insulation to keep any outside moisture out of the cabin and help keep things from wiggling.

Since most of my world is now connected with powerpoles, I like to have them near the battery. Lots of flexibility. Also if I need to mess around with the other end of the wiring, I can disconnect quickly from the battery without tools.

I got the version of the spray foam designed for electrical fuse boxes:

Edit: not my exact car, but this car audio dude used the same grommet. That's the hole I sleeved with vinyl tubing and then sprayed the foam around.

The sprayfoam is likely to break down over time in my experience. A rubber cable grommet would be less likely to fail.

I'm not sure if you've looked at it or not, but you might want to check the amp rating of your alternator. You've added several new loads to what was probably just above a marginal charging system with existing loads. If the extra batteries are discharged any appreciable amount, the load on the alternator is likely to be high enough to cause it to overheat and then components will fail. This is especially true if you're also running several other loads like lights/ac/defroster/etc.. Just saw that you have a current limiting device to charge the batteries, a very wise thing to do.

Some of the ford(and chevrolet) trucks and vans had dual alternator setups as an option. Installing them is usually plug and play with parts from the dealer.